In the area of the silver halide photographic light-sensitive material, high-sensitivity color light-sensitive materials have been developed with the advance of related techniques.
However, a light-sensitive material having a much higher sensitivity is demanded in specific uses such as indoor photography, astronomical photography and sports photography. Particularly in recent years, with the appearance of a camera having a much higher shutter speed, there has been increasing the demand for a light-sensitive material having a much higher sensitivity and a much better reciprocity law failure property in a short-time exposure under a high illuminance.
To satisfy this requirement, there have been conducted various studies to develop a light-sensitive material having a much higher sensitivity and a much better reciprocity law failure property in a short-time exposure under a high illuminance (hereinafter referred to as a high illuminance reciprocity law failure property).
In order to improve the high illuminance reciprocity law failure property, the present inventors have made a study on various phases of the problem including silver halide compositions and methods for manufacturing light-sensitive materials.
In the course of the study, close examinations were made to open a way for the technical improvement. And in microwave photoconductivity measurements of silver halide photographic light-sensitive materials which were made as an approach from the physical aspect, the present inventors found that there is a strong correlation between the intensity of a long-lived component in the microwave photoconductivity measurement and the high illuminance reciprocity law failure property.
This correlation is not yet theoretically interpreted, and its theoretical elucidation remains as a problem to be solved later.
But, the present inventors made a further study based on the above finding and, through the utilization of such a correlation, succeeded in making a silver halide emulsion excellent in high illuminance reciprocity law failure property by lengthening the life of photoconductivity.
It was also found in such a study that an emulsion comprised of core/shell crystal grains having a higher silver iodide content in the core portion than in the shell portion is one preferable example of emulsions for making a silver halide light-sensitive material having a high sensitivity and containing such a long-lived light component in the microwave photoconductivity measurement.
When a photographic light-sensitive material was prepared by use of such an emulsion, the high illuminance reciprocity law failure property was improved; but, as another problem, deterioration in photographic properties is caused by increase in fog due to aging in the interval between manufacture and use.